The invention is based on a wiper arm.
Known windshield wipers have a wiper arm which is constructed of a fastening element, secured to a drive shaft, that has a joint head; a joint part connected to the joint head via a toggle joint; and a wiper rod rigidly adjoining the joint part. The windshield wiper also has a wiper blade, which has a support bracket system and a wiper strip held by the support bracket system. The wiper blade is pivotably connected to the wiper arm in that a hooklike end of the wiper rod engages between two support cheeks of the support bracket system and surrounds a pivot pin. The joint thus formed guides the wiper blade with the wiper strip over a motor vehicle window; the joint part and the support bracket system make it possible for the wiper strip to adapt to a curvature of the vehicle window. A requisite contact pressure of the wiper strip on the vehicle window is attained with at least one tension spring, which braces the fastening element and the joint part jointly with the wiper rod via the toggle joint.
The fastening element is as a rule made from aluminum or die-cast zinc and is embodied as largely solid in its head and cone regions. A middle region of the fastening element has a U-shaped cross section, open toward the vehicle window, with reinforcing ribs.
To prevent the wiper arm in the preassembled state, before it is mounted on the motor vehicle, from collapsing in response to the spring force and thus to prevent the tension spring from coming unfastened, two side walls of the joint head extend in the longitudinal direction via the toggle joint and form two support faces, by way of which the joint part can be supported in the direction of the wiping area.
In known wiper arms, the fastening elements are often covered with a plastic cap that has a top wall and side walls, so as to protect the fastening element and its bearing points against soiling and corrosion and to obtain an attractively shaped component.
In order to make the cap in the hinged-open state secure against being lost and yet easily mountable and unmountable, the cap is pivotably supported on bearing faces that are closed over more than 180.degree. on bearing protrusions on the joint head. The bearing faces are formed by the face ends of the side walls. If the fastening element or the wiper arm is to be mounted on the motor vehicle or unmounted or adjusted, the cap can be hinged open on the side of the bearing point for the drive shaft. Via the more than 180.degree. closed bearing face, the cap is supported secure against being lost in the hinged-open state and can easily be slipped on by its open side or pulled off again.
To allow folding the cap open far enough, there is a recess in each of the side walls of the joint head that extend along the toggle joint; the cap can dip into this recess with its top wall when it is opened.
In the installed state on the motor vehicle, the tension spring generates the contact pressure of the wiper blade on the windshield. In the preassembled state, this force must be absorbed via a far shorter lever, from the toggle joint to the support face, and as a result a strong force acts on the support face. To allow securely absorbing this force in the joint head, the side walls must be made sufficiently high. In the region of the recesses, the cross section is weakened by the recesses and is more heavily loaded by notch stresses, which must be compensated for by a sufficiently high side wall below the recess. As a result, there are especially high side walls around the recesses.
Furthermore, the side walls of the joint head are made thicker than those of the remainder of the fastening element, so that the stresses around the toggle joint can be reliably absorbed. The greater material thickness, because of a uniform transition suitable for casting, extends up to the support faces.